The old methods of feeding high energy to high resistance loads in short times consisted primarily of Marx Generators, Pulse Forming Networks and Capacitor Banks. In general these devices are quite large and bulky and have low energy density (less than 100 joules per pound). This makes them undesirable for portable or airbourne operations.
An explosive magnetic field compression generator (e.g. strip line, helical, cylindrical, plate) directly converts chemical energy of high explosives to electromagnetic energy. This is generally accomplished by using explosive energy to drive metal conductors (referred to as armatures) against magnetic fields. The conversion efficiency (i.e., electromagnetic energy .div. explosive chemical energy), can be as high as 15%.
Since the energy contained in high explosive is large (2 megajoules/pound), the energy produced in the magnetic field can also be quite large. Using a large helical generator, up to four megajoules has been produced in magnetic field energy.
The field compression generator operates into a load that is normally inductive with negligible resistance. The key to obtaining good gain is to have a large ratio of initial generator inductance to load inductance. This puts an upper limit on the size of the load inductance, as the quantity of explosive needed for a large generator becomes impractical. In practice one is usually limited to inductive loads of order ten microhenries and less.
The load resistance must be kept below 0.1 to 1 ohm if a good energy gain is to be obtained. Resistance in the generator circuit introduces a damping effect which if too large will negate any gain produced by magnetic field compression.